Security is of paramount importance in software engineering. Nevertheless, security solutions are generally fitted into existing software as an afterthought phase of the development process. However, given the complexity and the pervasiveness of today's software systems, adding security as an afterthought leads to huge cost in retrofitting security into the software and further can introduce additional vulnerabilities. Furthermore, security is a crosscutting concern that pervades the entire software. Consequently, the manual addition of security solutions may result in the scattering and the tangling of security features throughout the entire software design. Additionally, adding security manually is tedious and generally may lead to other security flaws. In this context, the need for a systematic approach to integrate security practices into the early phases of the software development process becomes crucial. In this thesis, we elaborate an aspect-oriented modeling framework for software security hardening at the UML design level. More precisely, the main contributions of our research are the following: (i) We define a UML profile for the specification of security hardening mechanisms as aspects. (ii) We design and implement a weaving framework for the systematic injection of security aspects into UML design models. (iii) We explore the theoretical foundations for aspect matching and weaving. (iv) We conduct real-life case studies to demonstrate the viability and the scalability of the proposed framework
